Circuit interrupter arc extinguisher



Patented May 8, 1951 Z,551,&Z2

CIRCUIT INTERRUPTER ARC EXTINGUISHER Melvin Bingenheimer, East McKeesport, Eugene J. Walker, New Kensington, and Julius Toth, Beaver, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 80, 1947, Serial No. 794,622

6 Claims.

This invention relates to circuit breakers and more particularly to are extinguishers for dissipating and extinguishing the arc.

The principal object of the invention is to provide a simple and inexpensive, but efiective arc extinguisher for a circuit breaker.

A further object of the invention is to provide a circuit interrupter arc chute which is read- --i1y and cheaply blanked and formed in a punch press, and then easily handled and assembled without breakage into an arc extinguisher, which. gives off a minimum of inflammable gas and thus reduces arcing and increases the ability of the circuit interrupter to safely interrupt heavy currents.

Another object of the invention is to provide a circuit breaker with an arc extinguisher of the spaced magnetic plate type in which the housing for enclosing and supporting the plates is composed of coextensive composite sheet material comprising two adhesively bonded layers, one of which layers consists of a sheet of asbestos and the other layer comprises a supporting backing of a relatively rigid fibrous cellulosic material.

Another object of the invention is to provide a circuit breaker with an arc extinguisher of the spaced magnetic plates having an insulating housing for enclosing and supporting the plates composed of a composite sheet material comprising two adhesively bonded layers, one of the layers being composed of asbestos and the other layer consisting of a fibrous cellulosic material of sufficient stilfness to permit forming the composite sheet into the shape of the housing and to allow the plates to be fastened thereto and maintained in a predetermined osition.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to structure and operation, together with additional objects and advantages thereof will be best understood from the following detailed description thereof when read in conjunction with the accompanying drawing.

In said drawing:

Figure 1 is a side elevational view, partly in section, of a circuit breaker embodying the invention.

Fig. 2 is an enlarged perspective view of the arc extinguisher.

Fig. 3 is a plan view of the punching from which the arc extinguisher housing is formed.

Fig. 4 is an enlarged transverse sectional view of the arc extinguisher.

Fig. 5 is an enlarged sectional View showing the laminated housing material.

The present invention is illustrated as applied to a circuit breaker of the type disclosed in application Serial No. 592,804, filed May 9, 1945, by Melvin Bingenheimer and assigned to the assignee of this invention.

Referring to Fig. 1 0f the drawing, the circuit breaker comprises a housing I I and a cover plate l3 therefor, both constructed of molded insulating material, stationary contact means I5, movable contact means I'I, an operating mechanism I9 and a trip device 2 I.

The stationary contact I5 is rigidly secured to the inner end of a multi-angular terminal member 23 which is seated in an angular slot 25 in the molded housing II. The outer end of the terminal 23 is provided with a, connecting means 21 for connecting the terminal 23 in an electric circuit. At the opposite end of the housing II is disposed a terminal 29 which at its inner end supports the trip device (to be later described) and which is provided with a connector 38 at its outer end for connecting the terminal in an electric circuit.

The movable contact ll is rigidly secured on the free end of a U-shaped switch arm 31 having its legs Bl supported in recesses in the legs 55 of a U-shaped operating lever 35. The operating lever 35 is pivotally supported on a pivot pin 41 mounted in a suitable opening in the housing II and a matching opening in the cover 53. An operating spring 39 is connected under tension between the switch arm 3'! and a releasable carrier 33 pivoted on a pin M supported in companion openings in the housing I I and the cover l3. Spacers 43 are provided to maintain the carrier 33 properly spaced from the walls of the housing and the cover plate.

The operating lever 35 is provided with an operating handle 49 molded integral therewith and extending through an opening Si in the housing II. The operating lever is also provided with an arcuate member 53 molded integral therewith co-operating with the housing II to substantially close the opening 5! in any position of the handle 49. The switch arm 31 is electrically connected by means of a flexible connection 59 to one end of a bimetal element 45 forming a part of the trip device 2| and which is suitably secured, preferably by welding, to the inner end of the terminal 29.

The switch arm 31 is operated to manually open and close the contacts by manipulation ofthe handle 49. Movement of the handle in a clockwise direction from the full line position carries the legs of the switch arm 31 across to the left of the line of action of the operating spring 39 which then biases the switch arm to the open position and causes movement of the switch arm to open position with a snap action.

The contacts are manually closed b reverse operation of the handle. counterclockwise movement of the handle as from the 01? position to the on position moves the legs 5? of the switch arm 31 across to the right of the line of action of the spring 39 which thereupon acts to close the contacts with a snap action.

The circuit breaker is adapted to be tripped open instantaneously in response to the over-- loads above a predetermined value, or a short circuit, and after a time delay on lesser: overloads by means of the trip device 2 I. Operation of the trip device 2| releases the carrier 33 whereupon the overcenter spring moves the carrier clockwise moving the line" of action of the overcenter spring 39 to the right of the center line of the switch arm 3?. Thereafter the spring as acts to move the switch arm to open position with a snap action; The movement of the carrier 33 is arrested by engagement with a projection iii of the housing H.

The trip device 2I' comprises the bimetal element 4.5 connected bymeans of the flexible conductor 59 to-the switch arm 31, an electromagnet including a channel-shaped core member 65 and a movable armature t5, a latch element ST and a resilient member 69 rigidly secured to thebimetal element for supporting the armature 55. The terminal 29 is secured to the end wall of the casing l i by means of a screw l1 and the'bimetal element 55 is rigidly secured by suitable means such as welding to the upper inner end of the terminal29; Just below the point of attachment of the" bimetal element tothe terminal 29' the bimetalv element is formed inwardly at right angles and then downwardly fora short distance substantially parallel to' the terminal 29 to form a-flat surface to which the resilient member tg'is secured. The resilient member or spring 69 is secured to the bimetalelement by means: of a rivet 13. Below' the rivet 73 the bimetal extends downwardly at a. slight angle to the terminal 23. The lower endof the spring'fi'ii is looped as shown at (Fig. 1) and the upwardly extending end thereof carries an insulating button T! for insulating' the free end of the bimetal element 45 from the free end of the spring at.

The'channel-shaped core member 53 straddles the' bime'tal element 45 and is secured thereto preferably by welding. The armature 65 is secured to the spring. 69 adjacent the core member 63 by means of a rivet 8! which also serves to secure the latch element 6"! to the spring 69'.

The latch element t'l normally engages and restrains the carrier 33 in operative position as shown in Fig. 1. Upon the occurrence of an overload current below a predetermined value of, for instance, 1000% of normal rated current, the bimetal element t5 deflects moving its free lower end toward the right (Fig. 1). The bimetal' element lli, through the insulating button ll, moves the spring 5;!) in the same direction and causes the latch element St to release the carrier 33 whereupon the operating mechanism functions in the: previously described manner to automatically open the contacts.

Before the contacts can be closed following an automatic opening operation, it is necessary toreset andir'elatch the mechanism. This is; accomplished by moving the handle 49 clockwise to the full open position during which movement the leg 55 of the operating lever 35 engages a pin 82 in the carrier 33 and moves the carrier counterclockwise about its pivot li-i. Near the end of its counterclockwise movement, the free end of the carrier 33 wipes by the latch member 61, slightly flexing the spring 69. Thereafter the switch arm is moved to close the'contacts I5l'l inthe: previously described manner by movement of' the handle 59 counterclockwise to the closed position.

Upon the occurrence of heavy overload or short circuit, such for example as 1000% of rated current or over, the current flowing through the bim'etal' element t5 energizes the core member 63- a sufficient amount to instantaneously attract and operate the armature 65, releasing the carrier 3 3 and efiecting instantaneous opening of the contacts.

An important feature of the invention is the novel are extinguisher, indicated generally at 83, provided to quickly and safely extinguish the arc drawn when the current is interrupted.

The arc extinguisher 33' consists of a plurality of spaced arc splitting plates of magnetic material, shaped as more clearly shown in Fig. 4. Each plate has a slot of 8? formed therein and is provided with a plurality of lugs 89 whereby the plates may be rigidly attached to the sides of a U-shaped supporting and insulating housing or enclosure 91.

Heretofor'e arc extinguishers have, in some in stances, been provided with housings formed solely of fibre or cellulosic sheet material. Such materials, while possessing sufiicient mechanical strength to permit forming into the shape of the housing and to properly support the arc plates, have under certain conditions the undesirable properties of emitting gas and deteriorating when subjected to the heat of the arc. The heat of the are when confined to a relatively small space causes overheating of the fibre which emits gases due to the high temperature which when combined with the oxygen of the air may form a gas that is inflammable and may,. under certain conditions, constitute a hazard. Asbestos is one material that is free from these objectionable characteristics but doesnot have sufficient mechanical strength to permit'forming in punch presses into the shape of the housing or to permit rough handling in the shop during the assembly of the arc plates in their proper position.

Accordin to the present invention, the housing or enclosure 9| is formed of coextensive composite sheet material comprising two adhesively bonded layers of which one layer is composed of sheet asbestos or asbestos containin material and the other layer comprises a supporting backing composed of a relatively rigid fibrous cellulosic material. The rigid fibrous cellulosic material is of sufiicient stifiness' to permit forming of the composite sheet into the shape of the housing 9|, as illustrated in Fig. 2, and to allow the are plates 85 to be fastened theretoand maintained in predetermined position as by riveting over the ends of the lugs 89 against the composite sheet. Suitable materials for such cellulosic fibrous sheet are fish paper, press board and vulcanized fibre. Its thickness should be at least three mils. The asbestos sheet is composed of asbestos paper of a thickness of at least three mils.

The two layers may be adhesively bonded by glue, polyvinyl alcohol, starch adhesives or resinous coatings.

The housing 9I for the arc extinguisher is formed from the composite sheet of cellulosic material and asbestos by punching from the sheet a blank or punching 9Ia as shown in Fig. 3 of the drawing. The punching is scored along the lines 93 on the side comprising the fibre or cellulosic material so that the wings 95 which are to form the sides of the housing and the portion 9'! may be formed upwardly without breaking the fibrous supporting portion of the housing. Holes 99 are punched in the wings or side portions 95 to receive the lugs 89 of the arc plates 85. The wings or side portions 95 and the portion 91 are then formed upwardly at right angles to the base portion IUI with the asbestos on the inside and so that the holes 99 in the opposing side portions 95 are in alignment. Thereafter the plates 85 are assembled in the housing with the lugs 89 projecting through the holes 99 in the sides and the ends of the lugs are riveted or otherwise formed over to rigidly attach the housing thereto.

Referring to Fig. 1 of the drawing it will be seen that the casing II is provided with the projection BI and a transverse wall or partition I03. The side walls 95 of the arc extinguisher are each provided with recesses I01 and I99 which, when the extinguisher is assembled in the casing, cooperate respectively with the walls BI and H13 to retain the extinguisher in the proper position without positively fastening the extinguisher thereto. Also formed in the molded casing II is a channel I I l for the purpose of venting the hot gases generated when the arc is drawn. The channel III is somewhat less in width than the width of the interior of the casing as defined by the side wall of the casing and the cover plate I3. The base portion ID! of the arc extinguisher is provided with a projection I I3 which is formed to fit snugly within and projects into the channel I l I a sufiicient distance to protect the base of the channel from the hot gases.

The invention provides an improved arc extinguisher having a relatively thin housing comprising a composite sheet consisting of asbestos and a fibrous cellulosic material of sufiicient mechanical strength to support the arc plates and of relatively high heat resistance. The are extinguisher also has low gas emission characteristics. The improved arc extinguisher embodying the features and characteristics previously set forth increases the safe current interrupting capacity of the circuit breaker.

While the invention has been disclosed in acaccordance with the provisions of the patent statutes, it is to be understood that various changes in the structural details and arrangement of parts thereof may be made without departing from some of the essential features of the invention.

We claim as our invention:

1. A circuit interrupter including a casing and means for establishing an arc, an arc extinguisher for extinguishing the arc including a plurality of spaced slotted conducting plates, a U-shaped insulating housin at least partially enclosing said plates, said housing being formed from a single relatively thin composite sheet consisting of two adhesively bonded coextensive layers, one of said layers being composed of asbestos and the other of said layers comprising a supporting backing consisting of a relatively rigid fibrous cellulosic material, and said casing being provided with recesses and projections for receiving and 6.. supporting said housing Without said housing being positively fastened thereto.

2. A circuit interrupter including a casing and means for establishing an are, an arc extinguisher for extinguishing the are including a plurality of spaced slotted conducting plates, a generally U- shaped insulating housing comprising a base portion and integral side Walls at least partially enclosin said plates, said housing being formed from a single relatively thin composite sheet con sisting of two adhesively bonded layers, one of said layers being composed of asbestos and the other of said layers comprising a supporting backing consisting of a relatively rigid fibrous cellulosic material of sufficient stiffness to permit forming of said composite sheet into the shape of said housing and to allow said plates to be fastened to said side Walls and maintained in predetermined position, means defining a channel communicating said are extinguisher to the outside of said casing, and said housing having an integral portion extending into said channel.

3. A circuit interrupter including a casing and means for establishing an arc, an arc extinguishing means for extinguishing the arc including a plurality of metallic members, a U-shaped insulating housing comprising at base portion and integral side walls at least partially enclosing said metallic members, said housing being formed from a composite sheet consisting of a plurality of adhesively bonded coextensive layers, one of said layers being composed of sheet asbestos and the other of said layers consisting of a sheet of relatively rigid fibre of sufiicient stiffness to permit forming said composite sheet into the shape of said housing, and said casing having recesses and projections for receiving and supporting said housing without said housing being positively fastened thereto.

4. A circuit interrupter including a casing and means for establishing an arc, an arc extinguishing means for extinguishing the are including a plurality of spaced slotted plates, a U-shaped insulating housing enclosing at least three sides of said plates, said housing being formed from a relatively thin composite sheet consisting of a plurality of adhesively bonded coextensive layers one of said layers being composed of sheet asbestos of a thickness of at least three mils and the other of said layers consisting of a sheet of.

relatively rigid fibre of a thickness of at least three mils and of sufficient stiffness to permit forming said composite sheet into the shape of said housing, and said casing having recesses and projections for receiving and removably supporting said housing without said housing being positively fastened to said casing.

5. A circuit interrupter including a casing and means for establishing an arc, arc extinguishing means for extinguishing the are including a plurality of metallic members, a U-shaped insulating housing for supporting and at least partially enclosing said metallic members, means defining a channel for venting the hot gases generated by said arc to the outside of said casing, said housing being formed from a composite sheet consisting of a plurality of adhesively bonded coextensive layers, one of said layers consisting of asbestos and the other of said layers consisting of a fibrous cellulosic material, and said housing having an integral portion extending into said channel.

6. A circuit interrupter including a casing and separable contact means for establishin an are, an arc extinguisher for extinguishing the arc ineludinga plurality'ofspaced slottedrplates each of said plates beingprovidedwith a plurality of projections, a U-shaped insulating housing for at least partially enclosing said plates, said housing being formed from a flat composite sheet comprising, a. layer of asbestos and a coextensive layer of cellulosic material adhesively bonded together, said housing being punched in predetermined shape from said composite sheet and provided with integral portions forming side members having holes punched therein for receiving said-projections which are formed over to rigidly secure said plates to said housing, and. said casing. being provided with recesses and projections for receiving. and supporting said are extinguisher without said are extinguisher being positively fastened thereto.

MELVIN BINGENHEIMER.

EUGENEI J. WALKER.

REFERENCESv CITED The following references are of record in the file of this patent:

UNITED" STATES PATENTS 

